Wang Congyang, Wang Zhihui, Liu Lantao, Wang Chao, Liu Guangzhen, Xi Zhenfeng
Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China.
J Org Chem. 2006 Oct 27;71(22):8565-71. doi: 10.1021/jo061574a.
Fully or partially substituted 1-iodo- or 1-bromo-1,3-dienes could be readily lithiated using t-BuLi or n-BuLi to afford their corresponding 1-lithio-1,3-diene derivatives in quantitative yields. When these in situ generated lithium reagents were treated with organonitriles, depending on the substitution patterns of the butadienyl skeletons, substituted pyridines, pyrroles, and/or linear butadienyl imines were formed in good to excellent yields via N-lithioketimine intermediates. In the cases of 1,2,3,4-tetrasubstituted and 2,3-disubstituted 1-lithio-1,3-dienes, pyridine derivatives or linear butadienyl imines were generally formed depending on the reaction temperatures. When 1,2,3,4-tetrasubstituted 4-halo-1-lithio-1,3-dienes and 1,2-disubstituted 1-lithio-1,3-dienes were treated with organonitriles, pyrrole derivatives or linear butadienyl imines were obtained. Competition between 5-exo and 6-endo cyclization was found to be responsible for the formation of either pyrroles or pyridines. Selective elimination of RLi from the lithiated cyclic N-containing intermediates was observed. The order of elimination was found to be LiCl > Me3SiLi > LiH.
使用叔丁基锂或正丁基锂可轻松将全取代或部分取代的1-碘-或1-溴-1,3-二烯锂化，以定量产率得到相应的1-锂代-1,3-二烯衍生物。当这些原位生成的锂试剂与有机腈反应时，根据丁二烯骨架的取代模式，通过N-锂代酮亚胺中间体可高产率地形成取代吡啶、吡咯和/或线性丁二烯基亚胺。在1,2,3,4-四取代和2,3-二取代的1-锂代-1,3-二烯情况下，通常根据反应温度形成吡啶衍生物或线性丁二烯基亚胺。当用有机腈处理1,2,3,4-四取代4-卤代-1-锂代-1,3-二烯和1,2-二取代1-锂代-1,3-二烯时，可得到吡咯衍生物或线性丁二烯基亚胺产物。发现5-外向环化和6-内向环化之间的竞争是导致吡咯或吡啶形成不同产物的原因。观察到从锂化的含氮环状中间体中选择性消除RLi的现象。消除顺序为LiCl > Me3SiLi > LiH。
